High-molecular materials for use in high damping material compositions generally exhibit a typical viscoelastic behavior. When the materials vibrate from any cause, a complex sine strain (.epsilon.*) is generated on each material, and thereby a complexing stress (.sigma.*) is generated. A complex elastic modulus (E*) is a ratio of these as described in the following formula: EQU Complex elastic modulus (E*)=Complex sine stress (.sigma.*)/Complex sine strain (.epsilon.*)
A real part of the above complex elastic modulus (E*) is defined as a storage elastic modulus (E') relating to an elastic property of the high-molecular material. An imaginary part thereof is defined as a loss elastic modulus (E") relating to a viscous property of the high-molecular material. A loss tangent (tan .delta.) is a ratio of these as described in the following formula: EQU Loss tangent (tan .delta.)=Loss elastic modulus (E")/Storage elastic modulus(E')
The loss tangent (tan .delta.) is a one of factors for determining a sound and vibration damping feature, and therefore as the high damping material composition has a higher figure of the factor, a dynamic energy is absorbed and released in the form of electric or thermal energy, and the composition exhibits an excellent mechanical characteristics such as acoustic absorbing properties, or vibration-damping properties. A conventional high damping material composition is required to have a loss tangent (tan .delta.) of not less than 0.5.
The inventors of the present invention proposed a high damping material composition, which meets the above conventional prescribed property (tan .delta..gtoreq.0.5), prepared by blending a polymer having a polar side chain with a damping property imparting agent comprising a basic substance having at least one base selected from the group consisting of secondary amines, tertiary amines and heterocyclic compounds containing nitrogen. (Japanese Patent Application No. HEI9-362125)
Although the above high damping material composition satisfied the conventional prescribed property (tan .delta..gtoreq.0.5), it is desired for an environment for use thereof or a requirement for application that the high damping material composition exhibits a higher tan .delta. (tan .delta..gtoreq.2.0, more preferably tan .delta..gtoreq.2.5). Further, the damping property imparting agent may be crystallized or a bleeding (exudation) may take place due to dispersion thereof, and therefore the tan .delta. quickly declines, so that it can not keep a tan .delta. at the time of formation after a short period such as 2 weeks to one month, thereby losing its damping property. Moreover, the high damping material composition has a tan .delta. peak notably away from a room temperature at which the composition is supposed to be used most frequently. Thus, it is impossible to make the best use of the damping capability thereof under an environment desirable for use.